Its hard to see in the picture what it is because its fuzzy but if its staghorn look at my thread a couple down from yours. I used the excel treatment and it got rid of all of it and gave me my aquarium back. Since the treatment I started using the recommended on the excel bottle which is 5ml a day for a 55g aquarium and lowered my light. Non of it has come back. I was worried I was going to have to throw out all my plants but excel saved them.